If you mean the Trinity as described in the Athanasian Creed, I must confess that I do not understand the doctrine.
That said, I believe in the Father, the Son, and the Holy Spirit, the three being one God.
Which part are you having trouble with?
Maybe you'd have better luck with the understanding that comes via the Westminster Confession of Faith...
There is but one only, living, and true God: who is infinite in being and perfection, a most pure spirit, invisible, without body, parts, or passions, immutable, immense, eternal, incomprehensible, almighty, most wise, most holy, most free, most absolute, working all things according to the counsel of His own immutable and most righteous will, for His own glory; most loving, gracious, merciful, long-suffering, abundant in goodness and truth, forgiving iniquity, transgression, and sin; the rewarder of them that diligently seek Him; and withal, most just and terrible in His judgments, hating all sin, and who will by no means clear the guilty. Deut. vi. 4; 1 Cor. viii. 4, 6; 1 Thess. 1. 9; Jer. x. 10; Job xi. 7, 8, 9; Job xxvi. 14; John iv. 24; 1 Tim. i. 17; Deut. iv. 15, 16; John iv. 24, with Luke xxiv, 39; Acts xiv. 11, 15; James i. 17; Mal. iii. 6; 1 Kings viii. 27; Jer. xxiii. 23, 24; Ps. xc. 2; 1 Tim. i. 17; Ps. cxlv. 3; Gen. xvii. 1; Rev. iv. 8; Rom. xvi, 27; Isa. vi. 3; Rev. iv. 8; Ps. cxv. 3; Exod. iii. 14; Eph. i. 11; Prov. xvi. 4; Rom. xi. 36; 1 John iv. 8, 16; Exod. xxxiv. 6, 7; Heb. xi. 6; Neh. ix. 32, 33; Ps. v. 5, 6; Nah. i. 2, 3; Exod. xxxiv. 7. II. God hath all life, glory, goodness, blessedness, in and of Himself; and is alone in and unto Himself all-sufficient, not standing in need of any creatures which He hath made, nor deriving any glory from them, but only manifesting His own glory in, by, unto, and upon them: He is the alone fountain of all being, of whom, through whom, and to whom are all things; and hath most sovereign dominion over them, to do by them, for them, or upon them whatsoever Himself pleaseth. In His sight all things are open and manifest; His knowledge is infinite, infallible, and independent upon the creature, so as nothing is to Him contingent, or uncertain. He is most holy in all His counsels, in all His works, and in all His commands. To Him is due from angels and men, and every other creature, whatsoever worship, service or obedience He is pleased to require of them. John v. 26; Acts vii. 2; Ps. cxix. 68; 1 Tim. vi. 15; Rom. ix. 5; Acts xvii. 24, 25; Job xxii. 2, 3; Rom. xi. 36; Rev. iv. 11; 1 Tim. vi. 15; Dan. iv. 25, 35; Heb. iv. 13; Rom. xi. 33, 34; Ps. cxlvii. 5; Acts xv. 18; Ezek. xi. 5; Ps. cxlv. 17; Rom. vii. 12; Rev. v. 12, 13, 14. III. In the unity of the Godhead there be three persons, of one substance, power, and eternity; God the Father, God the Son, and God the Holy Ghost. The Father is of none, neither begotten, nor proceeding: the Son is eternally begotten of the Father: the Holy Ghost eternally proceeding from the Father and the Son. 1 John v. 7; Matt. iii. 16, 17; Matt. xxviii. 19; 2 Cor. xiii. 14; John i. 14, 18; John xv. 26; Gal. iv. 6.
CHAPTER II
Of God, and of the Holy Trinity